1. Field of the Invention
The present invention relates to an electromagnetic actuator having: a fixed core supported by a bottom wall of a housing made of magnetic material; a movable core arranged opposite to the fixed core via an air gap to drive a movable member; and coil assembly comprising a bobbin supported by the housing to surround the fixed and movable cores, and a coil wound around the bobbin.
2. Description of the Related Art
Such an electromagnetic actuator is already known as disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-1765.
In the electromagnetic actuator, characteristics of the movable member concerning thrust and displacement are dependent on an initial air gap between attracted surfaces of the fixed and movable cores, but the initial air gap may not be within the tolerance due to accumulated manufacturing errors of each part of the actuator. In the conventional one, for such an occasion, several types of coupling members with different length for coupling the movable member to the movable core have been prepared in advance and the air gap has been adjusted by replacing the coupling member.
However, such adjustment means for air gaps requires several types of coupling members, and moreover takes time and efforts in the replacement operation, so that the cost is inevitably increased.